Computer terminals and peripheral devices are now used in practically every aspect of life. Computer terminals come in all shapes and sizes and vary greatly in terms of function, power and speed. Additionally, the number of peripheral devices which can be attached to the computer terminals is increasing. Many peripheral devices exist such as printers, modems, graphics scanners, text scanners, code readers, magnetic card readers, external monitors, voice command interfaces, external storage devices, and so on.
Computer terminals and peripherals have become dramatically smaller and more portable. Personal computers and peripherals are small enough to sit on the desk at work. Smaller still are lap top computers and notebook computers. There are computer terminals which are small enough to be mounted in a vehicle such as a delivery truck or on a fork lift. Still smaller are the hand held terminals typically used for their portability features where the user can carry the computer terminal in one hand and operate it with the other.
Despite the reduction in computer size, the computer terminal still must physically interface with the peripheral devices. Thus, there must either be a cable running from one of the computer terminal to each device or the computer terminal must be docked with the device while the information transfer is to take place.
In the office or work place setting, the physical connection is typically done with cables. These cables pose several problems. If there are many peripheral devices, there must be many cables attached to the computer terminal. In addition to the eyesore created by all of the cables, the placement of the peripheral devices is limited by the length of the cable. Longer cables can be used but they are costly and do not alleviate the eyesore created by having cables running in all directions. Additionally, there may be a limited number of ports on the computer terminal thus limiting the number of peripherals that can be attached.
Another problem exists when there are several computer terminals which must share the same peripheral device such as a printer. All of the computers must be hardwired to the printer. As discussed above, long cables can fix this problem at least from a physical connection perspective but there still remains a protocol problem between the different computers. This problem is especially severe when the various computers are of different types such as a mixed environment of IBM""s and Macintoshes.
In the smaller computer terminal setting, the hand-held terminals and the portables, the cabling and connection problem can be more severe and cumbersome. Peripheral devices such as printers and scanners of all types have been reduced dramatically in size to match the smallness of the computer terminals. A notebook computer operator may wish to carry the computer and a cellular phone modem in a briefcase. Similarly, an operator may wish to have a hand- held computer terminal in one hand, a small portable printer attached to his belt, and a code reader in the other hand. The smallness of the computers and peripherals makes these demands possible but the required cabling makes these demands costly, inconvenient and even dangerous.
Physically connecting the computer terminals and peripherals severely reduces the efficiency gained by making the units smaller. An operator must somehow account for all of the devices in a system and keep them all connected. This can be very inconvenient. In the notebook computer and modem example, the operator may wish to have freedom to move around with the computer but without the modem. He may, for example, wish to work in various locations on a job sight and at various times transmit or receive information via his modem. If the modem and the computer are hard wired together, he must either carry the modem with him at all times or connect it and then disconnect it each time he wishes to use the modem. Similarly, the operator of the hand held terminal, code reader and printer will have the feeling of being all tied up while-using the three devices simultaneously when all three devices are connected with cables.
The physical connections created by cabling can be expensive because cables frequently prove to be unreliable and must be replaced frequently. In portable environments, cables are subject to frequent handling, temperature extremes, dropping and other physical trauma. It is not uncommon for the cables or the connectors for the cables on the devices to need replacing every three months or so. Additionally, all of the cabling can be dangerous. An operator who is using, holding or carrying several devices and feels all tied up is not just inconvenienced, he may be severely limited in his mobility and flexibility as he moves about the work area. This loss of mobility and flexibility directly undercuts the entire reason for having small and portable computers and peripheral devices and greatly increases the likelihood of operator injury while using the computer and peripheral devices.
Furthermore, as the cables wear out and break, which, as mentioned, happens frequently, there are dangers which are associated with the electrical current running through the cables. If the cable or connectors break, the current could shock the operator or create a spark which could cause a fire or even an explosion in some work environments.
Attempts to alleviate or eliminate these problems have been made but have not been greatly successful. One solution is to incorporate a computer terminal and all of the peripherals into one unit. However, this solution proves unsatisfactory for several reasons. For example, the incorporation of many devices into one unit greatly increases the size and weight, thus jeopardizing the portability of the unit. Furthermore, incorporating all of the functions into one unit greatly reduces and, in most cases eliminates, the flexibility of the overall system. A user may only wish to use a hand-held computer terminal at times, but at other times may also need to use a printer or occasionally a code reader. An all-incorporated unit thus becomes either overly large because it must include everything, or very limiting because it does not include everything.
Another solution has been to set up Local Area Networks (LAN""s) utilizing various forms of RF (Radio Frequency) communication. The LAN""s to date, however, have been designed for large scale wireless communications between several portable computer terminals and a host computer. Therein, the host computer, itself generally a stationary device, manages a series of stationary peripherals that, upon requests to the host, may be utilized by the portable terminals. Other large scale wireless communications have also been developed which for RF communication between several computer terminals and peripheral devices, but all proving to be ineffective as a solution. For example, these systems require the peripheral devices to remain active at all times to listen for an occasional communication. Although this requirement may be acceptable for stationary peripheral devices receiving virtually unlimited power (i.e., when plugged into an AC outlet), it proves detrimental to portable peripherals by unnecessarily draining battery power. Similarly, in such systems, the computer terminals are also required to remain active to receive an occasional communication not only from the other terminals or the host but also from the peripherals. Again, often unnecessarily, battery power is wasted.
In addition, such large scale systems are designed for long range RF communication and often required either a licensed frequency or must be operated using spread spectrum technology. Thus, these radios are typically cost prohibitive, prove too large for convenient use with personal computers and small peripheral devices, and require a great deal of transmission energy utilization.
Thus, there is a need for a radio frequency communication network that supports the use of network peripherals which solves the foregoing problems relating to power conservation and portability.
The present invention solves many of the problems inherent in present communication systems. The mobile network device participates as a slave to the first network pursuant to the first protocol and as a master to the second network pursuant to the second protocol, and resolves conflicts between the first and second protocols in communication systems having devices which use battery power. The present invention relates generally to local area networks and, more specifically, to a communication system for maintaining connectivity between devices on networks which have different operating parameters while limiting the power drain of battery powered devices.
In one embodiment of the present invention, a mobile network device has a single radio unit which is capable of participating in a first and second radio network which operate using a first and second communication protocol. The mobile network device participates as a slave to the first network pursuant to the first protocol and as a master to the second network pursuant to the second protocol, and resolves conflicts between the first and second protocols.
In another embodiment of the present invention, a mobile network device has a first radio transceiver for communicating with a main radio network and a second radio transceiver for communicating with a radio subnetwork. The mobile network device participates as a slave to the main radio network and participates as a master to the radio subnetwork.
In a further embodiment of the present invention, a mobile network device has a single radio unit capable of participating in a first and a second radio network. The first and second radio networks operate using a first and second communication protocol, respectively. The mobile network device participates as a slave to the first network pursuant to the first protocol and as a master to the second network pursuant to the second protocol, enters a state of low power consumption when not communicating with either the first or second network.
In another embodiment of the present invention, an RF local area network contains a first network device which uses battery power to transmit data to a second network device. In order to conserve power, the second network device determines a range value between the first and second network devices and transmits that value to the first network device so that the first network device can identify an appropriate, and potentially lower, data rate for subsequent transmission of data. The first network device may also consider its own battery parameters along with the received range value and identify an appropriate power level as well as data rate for subsequent transmissions.
In another similar embodiment, the second network device determines the range value between the first and second network devices and, based on the range value, indicates to the first network device an appropriate, and potentially lower, data rate for subsequent data transmission to the second network device. The second network device may also consider battery parameter information received from the first network device and use that information along with the range value to indicate to the first network device an appropriate power level, as well as data rate, for subsequent transmissions by the first network device.